Made weather agent dependent on user location

I'm not sure if this is the best way to do it... I have zero experience with huginn and haven't written much production Ruby. So feel free to make suggestions for improvements.
I wonder if we should just do `options['location'] = location`?  Then it would update it's options when it receives an event.

However, I still feel like a new Huginn user would expect the WeatherAgent, when receiving events, to immediately emit new events with the weather for that location, not reconfigure itself.  So, I think this new behavior would be a bit surprising for them.  Maybe I can try my hand at a ConfigurationAgent that reaches into other Agents and changes their configurations?  You could use this instead.  Give me a little bit ;)